Hectograph printing ink



atentecl Aug. 14, 1945 rmc'roeaarn PRINTING INK Nelson S. Knaggs, Cincinnati, Ohio, assigncr to Moore Business Forms, Inc., a corporation of Delaware I No Drawing. Application August 7, 1942, Serial No. 453,951

Claims.

This invention, while broadly relating to inks in general, has specific utility in connection with reproduction of copies by the hectograph. process.

The spirit hectograph process involves reproduction from a master sheet on solvent moistened copy sheets which take up dye from the master sheet carrying the hectograph ink by being brought into surface contact with the master sheet. Each copy sheet must be individually brought into surface contact with the master sheet and each copy takes a portion of dye away from the thin surface layer of ink until the ink on the master sheet will no longer give oif clean and clear copies. This improved ink is used to ink the letters or other characters on the master sheet and may be applied in any preferred manner known in the art. Also the copy sheets may be moistened by known methods, no special solvent being required. Any of the well-known commercial spirit solvents are satisfactory.

A leading object of the invention is to provide an ink for the master sheet which will greatly increase the number of copies which may be made and at the same time improve the clearness and non-smudging characteristics of the inked areas of the copies.

It is a further. object of the invention to provide an ink which facilitates the use of rotogravure and aniline presses for making master copies for hectograph reproduction.

Previous to this invention, master copies printed from so-called hectograph printing ink when used in the spirit process gave a maximum of several dozen bright legible copies. By the use of the improved ink as many as four hundred legible copies from the master sheet can be made before it is exhausted.

Known types of ink for hectograph reproduction prior to this invention consisted of methyl violet dye, glycerine, diethylene glycol and other suitable solvents. These ingredients were ground together on an ink mill and were compounded so that they would form an ink which would operate on a letterpress. The body of this ink was thick and viscous and quite similar to regular letterpress ink. Great care had to be taken in the use of these inks; the ink had to be printed in a heavy film in order to get any adequate number of copies and, therefore, the press had to be operated quite slowly due to smearing, smudging, and offset. The copies could not be handled for some time due to smearing. The inks also were hygroscopic and, therefore, on days when the humidity was high, considerable press trouble developed.

A further object is to provide a vehicle which is quite liquid and is compounded so as to be suitable for use in hectograph reproduction of higher speed than was possible with old and known letterpress type hectograph ink and there-- fore, much greater production can be achieved.

2. The thickness of the ink film on the master sheet can be controlled more accurately in the case of rotogravure printing by the variation of the depth of etch and the number of lines on the printing cylinder or plate. By these variations, the number of copies obtained from the master sheet can be greatly augmented.

3. The rapid drying of this new ink occurs without the film penetrating into the paper and thus full benefit of the dye in the film may be achieved.

4. The evaporation of the solvent which is the vehicle for the dye in the new ink, leaves a film which is practically pure dye. This eliminates the need of having a non-volatile vehicle which would remain in the printed film as in the case of older. type hectograph inks. Such a non-volatile vehicle had a tendency to make the ink penetrate into the paper stock upon aging, thus detracting from its duplicating power.

In addition to the many advantages. above pointed out in connection with use on rotogravure or aniline presses, this new ink has other surprising qualities constituting improvements over the old hectograph-inks. Thus the take-off, of the dye from the master sheet is retarded by means of retarding agents in small amounts up to about three per cent. Preferred retarding agents include film forming substances such as cellulose compounds, synthetic resins, natural resins, shellac, Vinylite, mazein and other film formtype of retarder used it has been found that a wide range 01 take-oi! properties in the ink film is attainable. For example; the amount and type oi retarding agent will change the properties 01 the ink so that the master copy can have an ink to exhaust its copying strength in the first one hundred copies; or it can be made to wear down slowly so as to obtain four hundred legible copies.

This invention is not necessarily limited to the above mentioned retarders. It has been found that the incorporation of any film forming substance such as those mentioned above may be employed in percentages of not more than approximately three per cent to control the rate of wear of the master oopy.

In previously known letterpress hectograph inks, the dye is ground into high boiling nonvolatile organic solvents which act as binding agents as well as the vehicle for the dye. Due to the fact that the ink contains a. high percentage of high boiling non-volatile organic solvents which do not volatilize at room temperatures of 20 C. to 25 C., the ink is easily smeared until the vehicle together with a large portion of the dye is absorbed by the paper. This absorption of the ink into the paper of the master copy decreases the number of copies which may be produced on the hectograph machine. Eventually the master copy is valueless due to this absorption into the sheet.

Experiments have shown that the rapid volatilization of the solvent from the printed film causes the dye to quickly crystallize on the surface of the sheet. The crystals interlock and aid the binding of the film to the paper. This binding action eliminates the necessity of using a high proportion of a non-volatile organic solvent as in the present letter-press types of ink. The elimination of high proportions of binding agents in the ink allows the use of a greater proportion of dye and, therefore, stronger copiescan be obtained. These experiments show a concentration of dye up to about 60% can be obtained. Also such high concentrations of dye have heretofore not been used in rotogravure or aniline press inks.

Unlike present day hectograph printing ink in which the dye must be ground into the vehicle, it has been further discovered that this new ink does not have to be ground in an ink mill. The ink may be manufactured by a simple mixing, the dye and retarding agent rapidly going into solution.

The following is a typical formula for a hectograph printing ink to be used in rotogravure or aniline printing in accordance with this invention.

Parts by weight Dye: Crystal violet dye 40.0 to 60.0 Retarder: Low viscosity nitrocellulose .1 to 3.0

High boiling point solvent: Cellosolve (ethylene glycol m o n o e t h yl ether) 10.0 to 15.0 Low boilin point solvent: Ethyl acetate 12.0 to 18.0 Low boiling point solvent: De-

natured alcohol 19.5 to 25.0

nitrocellulose in the solvents and then adding the dye with agitation until all is in solution.

This invention is not necessarily limited to the use of crystal violet dye, as other spirit soluble dyes of various colors may be used, for instance, methyl violet dye, ethyl violet, nigrosine base, malachite green, rhodamines, magentas and chrysoidine.

Any solvent or mixture of solvents may be used, which will dissolve the dye and retarding agent providing that the boiling points or boiling range are within the temperature limits of ordinary rotogravure or aniline press operations.. as say from 55 C. to 160 C. The boiling range can be varied by varying the proportions of the high boiling point and low boiling point solvents. A combination having a boiling range from 70 C. to C. is preferred. A mixture of solvents in the following proportion gives the preferred boiling range of from 70 C. to 135 0.:

Parts by weight It is preferable to have some of the solvent come on at a low temperature, and the high boiling solvents in the mixture should come oil. at an elevated temperature. The incorporation of the higher boiling solvents with the low boiling sol vent is effected to provide a vehicle for the ink which will not evaporate too quickly on the printing cylinders. Should this happen, the dye in the ink will tend to crystallize out on the press. This can be quickly corrected by increasing the proportion of high boiling solvent over that of the low boiling solvent.

Since certain changes in carrying out the above process, and certain modifications in the composition which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A hectograph printing ink having a, spirit soluble dye concentration wherein the dye content is in excess of approximately 39.5 per cent by weight, and containing a solvent for the dye and for the later mentioned retarding agent, said solvent having a boiling range substantially between 55 C. and C., the film transferring properties of said ink being augmented by incorporation therein of approximately 0.1 per cent to 3 per cent by weight of a film forming retarding agent.

2. A hectograph printing ink 'having a spirit soluble dye concentration wherein the dye content is in excess of approximately 39.5 per cent by weight, and containing a solvent for the dye and for the later mentioned retarding agent, said solvent having a boiling range substantially between 55 C. and 160 C.,.the film transferring properties of said ink being augmented by the incorporation therein of a retarding agent of the class or film forming solvent soluble material, in an amount'up to approximately 3 per cent by weight.

3. A hectograph printing ink having a spirit soluble dye concentration of a dye selected from the group consisting of crystal violet dye, ethyl violet, methyl violet dye, nigrosine base, malachite green, rhodamines, magentas and chrysoidine, said dye concentration having a dye content in excess of approximately 39.5 per cent by weight, said ink containing a solvent for the dye and for the later mentioned retarding agent, said solvent having a boiling range substantially between 55 C. and 160 C., the film transferring properties of said ink being augmented by incorporation therein of approximately 0.1 per cent to 3 per cent by weight of a film forming retarding agent.

4. A hectograph printing ink having a spirit soluble dye concentration of a dye selected from the group consisting of crystal violet dye, ethyl violet, methyl violet dye, nigrosine base, malachite green, rhodamines, magentas and chrysoidine, said dye concentration having a dye content in excess of approximately 39.5 per cent by weight and containing a solvent for the dye and for the later mentioned retarding agent, said solvent having a boiling range substantially between 55 C. and 160 C., the film transferring properties of said ink being augmented by incorporation therein of a retarding agent in an amount up to a maximum of approximately 3 per cent by weight.

5. A hectograph printing ink having a, spirit soluble dye concentration, and containing a solvent for the dye and for the later mentioned retarding agent, said solvent including a mixture of a plurality of different solvent materials respectively having high and low boiling points and including ethylene glycol monoethyl ether and denatured alcohol, the film transferring properties of said ink being augmented by the incorporation therein of approximately 0.1 per cent to r,

3 per cent by weight of a film forming retarding agent.

6. A hectograph printing ink having a spirit soluble dye concentration of a dye selected from the group consisting of crystal violet dye, ethyl violet dye, ethy1 violet, methyl violet dye, nigrosine base, malachite green, rhodamines, magentas and chrysoidine, said ink containing a solvent for the dye and for the later mentioned retarding agent, said solvent including a, mixture of 9. Flurality of different solvent materials respectively having high and low boiling points and including ethylene glycol monoethyl ether and denatured alcohol, the film transferring properties of said ink being augmented by the incorporation therein of a film forming retarding-agent in an amount up to a maximum of approximately 3 per cent by weight. Y

'7. A hectograph printing ink having a spirit soluble dye concentration, and containing a solvent for the dye and for the later mentioned retarding agent, said solvent including a mixture of cellosolve, ethyl acetate and denatured alcohol and having a boiling range substantially between C. and C., the film transferring properties of said ink being augmented by the incorporation therein of approximatehr 0.1 per cent to 3 per cent by weight of a film forming retarding agent. I

8. .A rotogravure or aniline type hectograph printing ink comprising from 40m 60 parts by weight of spirit soluble dye, from 0.1 to 3 parts by weight of a retarding agent, and a solvent for the. dye and retarding agent including a, mixture of different solvents respectively having boiling points of approximately 55 C, and C., said solvent mixture having from 5 to 30 parts by weight of the higher boiling point solvent and from 20 to 50 parts by weight of the lower boiling point solvent.

9. A rotogravure or aniline type hectograph printing ink comprising from 40 to 60 parts by weight crystal violet dye, from 10 to 20 parts by weight ethylene glycol mono ethyl ether, from 12 to 18 parts by weight ethyl acetate, from 19.5 to 25.0 parts by weight denatured alcohol and from .1 to 3 parts by weight low viscosity nitrocellulose.

10. A rotogravure or aniline type hectograph printing ink comprising substantially 58 parts by weight spirit soluble dye, not more than 1 part by weight low viscosity nitrocellulose, about 10 parts by weight ethylene glycol mono ethyl ether, about 12 parts by weight ethyl acetate and 19.5 parts by weight alcohol.

NELSON S. KNAGGS. 

